Chief science adviser to the US government's Operation Warp Speed, Moncef Slaoui, said that efforts are being made trying to understand discrepancies in data coming out of trials of AstraZeneca's experimental COVID-19 vaccine, CNN reported on Wednesday.
According to Slaoui, it might be possible to adjust the US trial arm if it turns out a different dose of the vaccine works better.
AstraZeneca had said that Phase 3 trial data from testing in Britain and Brazil indicated the vaccine was 62% effective, except for a batch tested in 3,000 volunteers that looked to be 90% effective in preventing infection.
This vaccine, developed with the University of Oxford, is also being tested in the US but there is no data from that arm of the trial yet.
In an Operation Warp Speed briefing, Slaoui said: "We are, of course, also reviewing in depth with the AstraZeneca and Oxford teams all the specifics of the data generated to understand what difference there is between a schedule that gives a 62% efficacy and one that gives 90% efficacy."
Reportedly, AstraZeneca said the stronger effects were seen in volunteers who got a half dose of the vaccine, boosted by a full dose a month later. The 62% efficacy was seen in the majority of volunteers who got the proper dosing for both shots.
Slaoui was quoted as saying: "We have been made aware of what's called now the half dose at the time it happened, was a change in the way the quantity of vaccine put in a vial was tested." He also said: "And when they realized there was an error or change in the approach, technique used, they corrected it. In the meantime, about 3,000 subjects were recruited, half in the placebo and half in the vaccine group."
According to CNN, Slaoui appeared to believe that the half dose was given by mistake.
The science adviser added: "What we're now looking to analyse is what immune response has been induced in those who have received the half dose and the full dose versus those that have received twice the full dose and understand whether there are differences in the immune response induced."
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